The general procedure for the synthesis of 2-amino-3-methyl-5-nitropyridine from 2-amino-3-methylpyridine was as follows: 3-methylpyridin-2-amine (5.0 g, 46.2 mmol) was dissolved in concentrated sulfuric acid (24 mL) and the mixture was cooled to 0 °C. At the same time, fuming nitric acid (density = 1.5, 3.5 mL) was cooled to 0 °C. Concentrated sulfuric acid (3.5 mL) was slowly added dropwise to the reaction mixture while keeping the temperature below 20°C. Subsequently, the stirred mixture was gradually warmed to 20 °C and transferred to a second flask in 3-5 mL batches. The second flask was heated to 35-40°C (note: the temperature should not exceed 40°C and the temperature should be carefully monitored after each addition of a new batch). Next, the reaction mixture was continued to be stirred at 50°C for 30 minutes. Once the reaction is complete, the mixture is cooled to room temperature and neutralized with concentrated ammonia. At this point, a precipitate is generated, which is filtered and washed sequentially with water and 50% aqueous DMFA (6 mL). Finally, the product was purified by recrystallization from DMFA to give 3-methyl-5-nitropyridin-2-amine (2.52 g, 35% yield).
